Abstract: Based on the neural point overcurrent protection action of converter transformer grid side which occurred during system tests at a certain UHV converter station, the protection action signal received at monitoring center is checked and the data sampling and fault recording waveform of the protection device are analyzed; the secondary current circuit is checked and TA test is carried out after the power-off to find out the fault origin; the cause of the fault is analyzed and the fault is disposed, meanwhile, the design suggestion is made based on this failure situation.